This invention relates to time-division switching systems and more particularly to arrangements for improving the efficiency of communication path completion through such systems.
One type of known time-division switching system, referred to as a time-space-time (TST) system, comprises a first buffer memory stage, a space-division switching stage, and an output buffer memory stage. Data words representative of speech signals are received by the system, stored in the first buffer memory, selectively read from the first buffer memory and transmitted through the space-division network to the output buffer memory. In certain of these known time-space-time switching systems, such input port of the space-division network is uniquely associated with a first buffer memory and each output port of the space-division network is associated with a unique output buffer memory.
One time-division switching system of this last-mentioned type is described in the application H. E. Coonce et al., Ser. No. 701,604, filed July 1, 1976 now Pat. No. 4,064,370. In accordance with the H. E. Coonce et al., arrangement, data words are organized by the switching system in individual channels of one of a plurality of time-multiplexed lines. These data words are transmitted to and stored in a predetermined one of a plurality of intermediate buffer memories. The buffer memory, in which a given data word is stored, is predetermined by a fixed assignment algorithm. Also in accordance with the H. E. Coonce et al., arrangement, data words from the two parties of a call are communicated bi-directionally through the space-division network during the same time slot. That is, data words representing the signals from two communicating parties are read from their associated intermediate buffer memories and transmitted through the network to the two associated output buffer memories during the same time slot. Such a switching method can be maintained since available paths through the space-division network are assigned in a mirror image manner.
Occasionally, data words respresenting signals from both parties are stored, in accordance with the fixed assignment algorithm, in the same intermediate buffer memory. This is referred to as an intrabuffer call. When this occurs, bi-directional communication must employ two time slots since a given intermediate buffer memory can be accessed only once per time slot. The use of two time slots for the intercommunication of the two parties reduces the efficiency of the time-division switch and increases the central processor time required to control the switching system. It is an object of the present invention to reduce the number of conversations requiring two network time slots for intercommunication and to thereby increase the efficiency of the switching system.